Ostler: Giants’ hot streak will be tested by hot weather

Matt Duffy (5) is congratulated by teammates in the dugout after hitting a two-run homerun in the first inning as the Giants played the Oakland Athletics at AT&T Park in San Francisco, Calif., on Sunday, July 26, 2015. The Giants won 4-3.

Matt Duffy (5) is congratulated by teammates in the dugout after...

Postcards from the windup game of the Bay Bridge weekend ...

The Giants have three more games this week to fatten up before they embark on the Stretch of Death. Or as they call it in Latin America, El Stretcho de Muerto.

Thirty-two games in 34 days against high-level opponents in a lot of hot summer ballparks will test the Giants’ mettle and deodorant.

It starts Friday with a roadie to hot Texas, Hotlanta and hot Chicago. El Stretcho includes four against the hot Nationals, six against the blazing Cardinals, and winds up with three in Los Angeles against the hotheaded Dreadeds.

All that and global warming, too.

•Fortune-wise, the Giants are starting to look like the Warriors. Good stuff happens on a regular basis.

The Giants sweep the A’s with Sunday’s 4-3 win, move closer to the Dodgers, win their 11th in the last 12 games, and treat 40,000-plus to a vitamin-enriched sunny day and free cornball cowboy hats. Yee-haw.

•On free-cowboy-hat day, Cowboy Joe West worked the 4,768th game of his umpiring career. That ties him for No. 3 on the all-time list, behind Bill Klem (5,369) and Bruce Froemming (5,163). But you knew that.

•A lot of the traditional stats have been devalued by the crush of sabermetrics. But BA is still meaningful, and the old .300 mark is still a respected standard of excellence.

Matt Duffy stepped to the plate in the first owning a .299 average. He got a 2-0 high fastball from Kendall Graveman and slammed a two-run homer to left. That moved Duffy to .301, and he might never look back. The human coat rack singled home another run in the second and finished the day batting .302.

Random stat: Duffy hit 13 minor-league homers his first three seasons, in 942 at-bats. He has nine homers this season in 305 at-bats.

The Giants are worried, at least a tiny bit, about how the rail-thin Duffy will hold up over the last two months of the regular season. He did tell me he’s very aware of his need to conserve energy for the stretch run in the hot months.

On Sunday, for instance, Duffy did not run in the San Francisco Marathon.

•Defense. The Giants play it, the A’s don’t.

Gregor Blanco and Joe Panik robbed Billy Burns of hits. Duffy made a nice play on a slow roller to third. Buster Posey gunned down two would-be base stealers.

The A’s seemed to be fielding a slippery ball.

It’s just one game, but in general, the Giants are a first-rate defensive club, and the A’s are a 30th-rate defensive club. That helps account for the A’s 10-24 record in one-run games.

Four hits Sunday for a mini-mart 7-for-11 for the series. And those two gun-downs. In the fourth, Posey stretched a hit to right into a double, slapping his helmet on tight as he rounded first and challenged Josh Reddick’s arm.

In the seventh inning, Posey slid hard into second trying to break up a double play.

Posey is hitting .328, on a pace to approach the numbers of his 2012 MVP season when he led the league in batting at .336 and had 24 homers and 103 RBIs.

When you’re hot, you get some luck, and stuff is dropping in for Posey. But he is more of a first-ball opportunist this season, only 33 whiffs (Brandon Belt has 95), putting the ball in play via dump, squib, blast, poke, pull and pound.

•The bay’s other fine catcher, Stephen Vogt, is quietly edging in the other direction, 0-for-4 Sunday, now batting .274. Twice he got shifted, grounding out to Panik playing in short right.

•Everything you need to know about the difference between the Giants and A’s you can learn from the MLB jersey sales Top 20. The Giants check in with Madison Bumgarner No. 1, Posey No. 3 and Hunter Pence No. 6.

The list goes only 20 deep, but I’m guessing the A’s wouldn’t have anyone in the top 50. Sonny Gray or Vogt maybe. With the A’s, if you get good, you get gone.

Ben Zobrist re-punched his ticket out of Oakland with two singles in his first two at-bats, after hitting for the cycle over the first two games of the series. He might be shipped out by the time you read this. So think twice before buying his jersey.